Tuesday’s election ensures that President Barack Obama’s health care law marches on — but once again, its success is at the mercy of the states.

Whether the Affordable Care Act eventually manages to expand coverage to 30 million-plus people will largely depend on whether states opposing the massive overhaul will now accept the law’s inevitability and set a path for getting it up and running within their borders. And states are going to have some major deciding to do in a short amount of time.

Eight days, to be exact.

By Nov. 16, states must tell the Obama administration whether they plan to run at least part of their own health insurance exchanges, new state-based marketplaces that will provide subsidies for low- and middle-income individuals and small businesses to purchase coverage. Eventually, states also will have to decide whether they’ll accept a larger expansion of Medicaid, which comes with a generous match from the federal government but still requires states to pony up some of their own money.

Carrying out the 2010 health care law successfully was always going to depend on states cooperating with the feds to get the law’s many pieces in place. But virtually all the Republican-led states have resisted committing to an exchange, hoping the Supreme Court or last night’s election would deliver a knockout blow to Obamacare.

That defeat never came, and GOP governors face a soul-searching decision they’ve seen coming since earlier this year: Do they take ownership of the law, although opposition has become a bedrock principle of Republican Party? In states that don’t create those exchanges, the feds will step in and run them. And that’s an arrangement that the Obama administration and health insurers who’ll sell in the new marketplaces aren’t particularly thrilled about.

Though most Republican states said they were waiting on election results to make their formal decision on exchanges, a number have been actively planning behind the scenes to run their own if options for the ACA’s demise were all exhausted.

“I think you’ll see a large number of states that have been waiting to begin to move more aggressively to implement,” said David Merritt, managing director at Leavitt Partners, which advises red states on exchange implementation.

So far, just 13 states and the District of Columbia have told HHS they plan to control their own exchange. In all, two-thirds of states could be ready to run at least part of an exchange when they open for enrollment next October, predicts Joel Ario, former HHS director of exchange planning. At least five GOP governors — including Texas’s Rick Perry, Florida’s Rick Scott and Louisiana’s Bobby Jindal — have absolutely rejected setting up their own exchange.

“My best guess is that every other state is in some state of preparedness,” Ario said. That includes some states where the governors have been outspoken about how much they dislike the law.

But even for the states most enthusiastically working to set up the new insurance marketplaces, plenty of questions remain. Leading up to the election, the Obama administration has sat on key rules governing exchanges, the benefits that health plans must cover, employer requirements and the Medicaid expansion. And stakeholders, including the health insurers, face remarkably short deadlines to prepare for the core coverage expansions and consumer protection to go into effect in 2014.

“We’re hoping to see proposed rules as soon as possible,” said Justine Handelman, vice president of legislative and regulatory policy for the Blue Cross and Blue Shield Association. “We’re now less than a year from open enrollment.”

Countless questions from Republican and Democratic governors, lawmakers and the industry to the Obama administration have gone unanswered since the Supreme Court upheld most of the health law on June 28. The court decision also added a new wrinkle in the ongoing struggle between the federal government and the states by making the law’s massive Medicaid expansion — which accounts for millions of the newly insured — voluntary.

HHS hasn’t yet indicated how flexible it will be on letting states accommodate the new Medicaid populations. Governors across party affiliations have expressed reservations about expanding a program that commandeers a growing portion of their state budgets, but many watching the states believe the law’s 100 percent federal funding for the newly eligible enrollees through 2016 is too good a deal to pass up.

The most seasoned Republican governors on health policy have already eyed the Medicaid expansion as an opportunity to press the feds to approve reforms favored by the GOP, like health savings accounts and greater leeway on installing co-pays. But it remains to be seen how much the Obama administration is willing to bend to ensure broader participation in the ACA.

The Obama administration is “going to have to give states some greater certainty that the money is going to be there, that the flexibility is going to be there,” said Licy Do Canto, a health care lobbyist who works on Medicaid issues.

HHS hasn’t set a deadline for states to declare whether they’ll opt in to the Medicaid expansion, but it’ll get plenty of attention when state legislatures convene in 2013.

One of the most interesting dynamics to watch going forward is how Republican-led state legislatures will cope with the reality of Obamacare’s survival. While several Republican governors over the past couple of years have pushed to set up their own exchanges, strong pushback from Republican state lawmakers has killed off those plans.

“Whether you’re going to do a state-based [exchange] or not, you have to engage in some respect because it’s going to be operating in their states,” said Joy Johnson Wilson, health policy director for the National Conference of State Legislatures. “I think it’s going to be interesting to see how many are willing to sit back and be the passive partner.”